Removal of fasteners from a workpiece often becomes an unpleasant and time consuming task when the fastener is held fast and sufficient force cannot be applied to overcome a fastener retaining force (also referred to as a cohesive force) to effect removal. The retaining force is great when the fastener becomes rusted in place, the workpiece or the fastener have expanded or contracted or a power tool, e.g., a hydraulic, pneumatic or electric powered tool, has been used to tighten the fastener.
Penetrating oils are used to dissolve rust to facilitate removal but are not effective if the reason for the great retaining force is not the presence of rust.
Alternatively, the power tool can be used to try to overcome the retaining force. Unfortunately, the power tool does not apply a rotational and linear forces simultaneously to the seat of the fastener. If the rotational force required to overcome the retaining force is greater than the force that the seat can withstand, the power tool strips the seat making removal of the fastener even more difficult.
Hand tools can also be used to remove the fastener; but again only apply a rotational force to the fastener. As with the power tool, if the rotational force required to overcome the retaining force is greater than the force that the seat can withstand, the hand tool will strip the seat rendering removal even more difficult.
With hand tools the force required to overcome the retaining force often cannot be generated without the use of a lever. When the fastener is finally and suddenly freed, the person cannot reduce the force applied to the lever quick enough which results in injury to the person, such as scraped knuckles, which is an unpleasant experience.
The fastener can be struck in an attempt to loosen it. However, immediately after impact, there is no longer any force applied and any beneficial effect of the impact dissipates prior to applying a rotational force.
The action of almost all available tools for tightening and unwinding of threaded fasteners relegates to three cases which we illustrated in FIGS. 1A, 1B and 1C. First, the application of one rotating force vector by a lever with one shoulder (FIG. 1A). Second, the application of a couple of rotating forces by a lever with two shoulders situated vis-a-vis on the center of symmetry of the rigid body (FIG. 1B). Third, the application of resultant vector rotating forces, plus force directed perpendicular down on the seat of the body (FIG. 1C).
In all three cases we have a sum cohesion force that is present and which acts against the rotating forces. Up to the moment of stretching, loosening and unwinding of the fastener, we have equilibrium of a rigid body, i.e., the fastener. The term equilibrium implies that the body is either at rest or its center of mass moves with constant velocity. We shall deal with a body at rest, i.e., a body in static equilibrium.
One necessary condition for equilibrium is that the net force on the body must be zero, and the body must have no tendency to rotate. This second condition of equilibrium requires that the net torque about any origin must be zero. In order to establish whether or not a body is in equilibrium, we must know the size and the shape of the body, and the points of application of the various forces.
The bodies that we discuss here, such as threaded fasteners, are assumed to be rigid. A rigid body is defined as a body that does not deform under the application of external forces. That is, all parts of a rigid body remain at a fixed separation with respect to each other when subjected to external forces. In reality, all bodies will deform to some extent under load condition. Such deformations in some cases are small and will not affect the conditions of equilibrium.
Consider a single force F acting on a rigid body that is pivoted about an axis through the point O as in a FIG. 1A. The effect of the force on the body depends on its point of application. If r is the position vector of this point relative O, the torque associated with the force F about O is given by: EQU .tau.=r .times.F
It is well known from the course of physics that the vector is perpendicular to the plane formed by r and F. Furthermore, the sense of .tau. is determined by the sense of the rotation that F tends to give to the body. The right-hand rule can be used to determine the direction .tau.. As can be seen from the FIG. 1A, the tendency of F to make the body rotate about an axis through O depends on the moment arm d (the perpendicular distance to the line of action of the force) as well as on the magnitude of F. By definition: EQU .tau.=F.times.d
Now suppose two equal and opposite forces act in the directions shown in FIG. 1B, such that their lines of action do not pass through the center of mass. Such a pair of forces, acting in this manner form what is called a couple. Since each force produces the same torque, i.e., F.times.d, the net torque has a magnitude 2.times.F.times.d. It is clear, the body will undergo an angular movement about the axis. This is a nonequilibrium situation as far as the rotational motion is concerned. The "unbalanced" or net torque on the body gives rise to an angular acceleration according to the relationship: EQU .tau..sub.net =2F.times.d-l.times..alpha..
In general, a rigid body will be in rotational equilibrium only if its angular acceleration is zero. Since .tau..sub.net -1.times..alpha., for rotation about a fixed axis, a necessary condition of equilibrium for rigid body is that the net torque about any origin must be zero. So, we have two necessary conditions for equilibrium, which can be stated as follows:
(1) The resultant external force must be zero .SIGMA.F=O PA1 (2) The resultant net torque must be zero about any origin .SIGMA.F=O .SIGMA..tau.=O
Return to the case of FIG. 1B, we have F.sub.rot +F.sub.rot +F.sub.coh =O to satisfy the conditions for equilibrium, and also .tau..sub.net =O.
Consider the case of FIG. 1C it is clear that .SIGMA.f.sub.i =O, and .tau..sub.net =O, but in this case the forces are more in number.
The turning of the body using different tools that are classified in one of the above-described figures is a violation of the conditions of equilibrium, due to the overcoming of cohesive forces F.sub.coh by overpowering rotating forces.
In FIG. 1A, the unwinding of a stubborn object can be realized only if F.sub.rot becomes greater than F.sub.coh, so that according the equation F.sub.rot +F.sub.coh =O, it becomes not equal O, and .tau..sub.net .noteq.O. This can become true either by increasing the magnitude of F.sub.rot or by extending the moment arm d of F.sub.rot or by decreasing F.sub.coh. The respective tool experiences insuperable obstacles, first the increase in F.sub.rot is limited, because of limited hand muscles strength, and the increased risk for trauma or broken body if the tool slips. Second, increasing d meets with the limitations of access and requires more free room for applying the tool to, and the turning of, the body, which in most cases is impossible. Decreasing F.sub.coh can be accomplished either by using a penetration oil or by stretching and pressing the helixes of the threads of a fastener and the workpiece, which cannot be accomplished with these kinds of tools.
In FIG. 1B, when couple rotating forces are applied, the situation is similar, but every increasing in F.sub.rot or d, leads to double increasing of .tau. so that tools acting this way have some advantages in comparing with the tools represented by FIG. 1A, if it concerns tight areas.
Now lets analyze the third case, shown on FIG. 1C, where we have equilibrium, so .SIGMA..sub.i f.sub.i +F.sub.imp +F.sub.coh =O where i=1,2, . . . 12 and .tau..sub.net =.SIGMA..sub.i f.sub.i .multidot.d.sub.i +F.sub.imp .multidot.x+F.sub.coh.multidot.d=O.
If we account that f.sub.1 =f.sub.2 =. . . =f.sub.i & d.sub.1 =d.sub.2 =. . . =d.sub.i =d, then, .SIGMA..sub.i f.sub.i .times.d.sub.i =i.times.f.times.d.
In this case the overcoming of the equilibrium is much easier, in spite of the fact that f has a smaller amplitude and d is much smaller than in the previous two situations, because we have multiforce action and on the other hand the action of F.sub.imp, strongly decreases the amplitude of the F.sub.coh, so unwinding of stubborn objects by these devices are much easier.
U.S. Pat. No. 3,158,050 to Shandel discloses a rotatable impact wrench having a cross arm 2 held in position on a spindle 1 by a spacer sleeve 9. The cross arm 2 is rotated to contact abutment lugs 11 on diametric flange 4 to apply a rotational force to a socket 3 which is placed over a nut. The diametric flange 4 with abutment lugs 11 is not Y-shaped or V-shaped. Further, the cross arm 2 only rotates and cannot provide a linear force because it is held in linear position by the spacer sleeve 9.
U.S. Pat. No. 4,628,776 to Witbeck only provides rotational force and lacks a Y-shaped or V-shaped element.
U.S. Pat. No. 4,759,272 to Andersson is directed to a device in impact wrenches which lacks a Y-shaped or V-shaped element.
French Patent No. 648,559 discloses a U-shaped device in the figures and therefore fails to disclose a Y-shaped or V-shaped element.
Further, there is no teaching in Shandel, Witbeck, Andersson or the French patent of a structure to which a sudden, sharp impact force is applied to remove a fastener.
A system for transferring a linear force to rotational and linear forces that are applied a fastener to cause rotation, and preferably removal, of the fastener which overcomes one or more of these shortcomings is desirable.